A method for constructing a universal obstacle-avoiding vortex acoustic tweezers that can bypass objects of any shape

Abstract

The present invention proposes a technology for constructing a universal obstacle-avoiding vortex acoustic tweezers that can bypass objects of any shape. The obstacle avoidance trajectory is designed according to the segmented obstacle contour, and the phase of the line sound source is controlled based on the caustic method to form a self-bending beam that propagates along a predetermined trajectory. The phase control of the one-dimensional sound source is extended to two-dimensional space, and an annular phase screen is constructed to achieve two-dimensional phase control of the annular array of planar fan-shaped transducers. The self-bending beam is rotated along the axis to construct a universal obstacle-avoiding vortex acoustic tweezers that can bypass objects of any shape. The present invention can guide the phased sound waves output by the annular array of planar fan-shaped transducers to bypass obstacles of any shape along a set trajectory, and then construct a vortex acoustic tweezers with higher positioning accuracy and control capabilities, and minimize the reflection and absorption of sound waves by the obstacle, significantly improving the sound pressure and sound radiation force in the focal area of the sound field, and realizing accurate, flexible and efficient obstacle avoidance object control.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultrasonic manipulation, and in particular relates to a method for constructing universal obstacle-avoiding vortex acoustic tweezers that can bypass objects of any shape. Background Art

[0002] Vortex acoustic tweezers, with their spiral phase wavefront and central acoustic pressure zero point, can exert acoustic radiation forces and torques on objects, enabling contactless capture, movement, and rotational manipulation. Compared to optical tweezers, which can only penetrate transparent objects, vortex acoustic tweezers have superior penetration, and their mechanism of action is independent of the target's optical, electrical, or magnetic properties. They are non-invasive, radiation-free, and biocompatible, offering promising applications in biomedical applications such as chiral drug separation, multimodal imaging, and targeted drug delivery.

[0003] However, in practice, acoustic scattering from obstacles such as bones and tissues can easily affect the spiral phase wavefront of the vortex acoustic tweezers, thereby weakening or even destroying their formation. Although researchers have proposed that the curved trajectory of a self-bending beam can be used to construct vortex acoustic tweezers with an obstacle-avoidance cavity, the specific curved trajectory of the transverse self-accelerating wave requires a zero sound pressure region at the center of the transducer, and the shape of the obstacle-avoidance cavity formed is relatively fixed, which greatly reduces the accuracy and efficiency of obstacle-avoidance vortex acoustic tweezers and limits their further development and application.

[0004] Therefore, it is necessary to propose a new obstacle-avoiding vortex acoustic tweezers construction technology so that the obstacle-avoiding vortex acoustic tweezers can fully utilize the sound source, improve the efficiency of the obstacle-avoiding vortex acoustic tweezers formation, overcome the defect that the transverse self-acceleration beam trajectory is difficult to control, bypass irregular obstacles, improve the accuracy and flexibility of the obstacle-avoiding vortex acoustic tweezers formed, and realize obstacle-avoiding object control for obstacles of arbitrary shapes. Summary of the Invention

[0005] Technical problem to be solved: Vortex acoustic tweezers can achieve point-to-point capture and rotational manipulation of objects without contact, and have received widespread attention in biomedical applications. However, acoustic scattering from obstacles such as bones and tissues can destroy the spiral wavefront of the vortex acoustic tweezers, making it difficult to perform stable object manipulation at the desired position. Although the vortex acoustic tweezers based on transverse self-accelerating waves have an obstacle avoidance cavity and can achieve obstacle avoidance object manipulation, it is necessary to retain a zero sound pressure area of a certain radius at the center of the transducer, and the cavity shape is relatively fixed, which is difficult to match the actual obstacle, resulting in the formed vortex acoustic tweezers having problems such as insufficient positioning accuracy and low energy transmission efficiency.

[0006] Technical solution:

[0007] A method for constructing a universal obstacle-avoiding vortex acoustic tweezers capable of bypassing objects of any shape, the method comprising the following steps:

[0008] S1, for obstacles with arbitrary shapes, a segmented polyline circumscribed to their contours is designed to construct a self-bending beam trajectory;

[0009] S2, based on the caustic theory, designs the initial phase distribution of the one-dimensional line sound source according to the position of each line segment in the segmented polyline, forming a self-bending beam with a preset curved propagation trajectory;

[0010] S3, rotate the phase distribution of the one-dimensional line sound source in step S2 along the axis to construct a two-dimensional phase distribution, design an annular phase screen to control the phase of the planar sector transducer annular array, perform initial phase encoding on each sector of the transducer array, and form a universal obstacle-avoiding vortex acoustic tweezers that can bypass objects of any shape.

[0011] Furthermore, in step S1, the process of constructing the self-bending beam trajectory includes the following sub-steps:

[0012] Randomly select M points on the known obstacle contour trajectory Ω and draw tangent lines through these points to the obstacle contour trajectory Ω;

[0013] Connect adjacent tangents to obtain a segmented broken line Ω′ containing M segments, which is completely tangent to Ω. The segmented broken line Ω′ is completely outside the obstacle contour trajectory Ω. The larger M is, the higher the matching degree between the obstacle avoidance cavity and the obstacle contour is. M is not less than Where L is the radius of the sound source and λ is the wavelength.

[0014] Furthermore, in step S2, the process of designing the initial phase distribution of the one-dimensional line sound source according to the position of each line segment in the segmented polyline includes the following sub-steps:

[0015] According to the segmented broken line Ω′, calculate the intersection S of the tangent line of the mth segment and the sound source m ;

[0016] Based on the caustic method, calculate S m The initial phase sequence φ corresponding to the sequence m :φ m =-k0D m , where k0 represents the wave number, D m Represents the mth line segment and S m The distance between points;

[0017] The discontinuous distribution S m Continuation, specifically, the initial phase sequence φ m Upsampling is performed to obtain the initial phase distribution of any point on the line sound source.

[0018] Furthermore, the sound pressure p of the self-bending beam generated by the initial phase control of the one-dimensional line sound source OA at any point P in space is expressed as:

[0019]

[0020] Where u represents the particle velocity on the line sound source OA, R represents the distance between point P and the line element dx, ω = 2πf represents the angular frequency, L is the radius of the sound source, k0 represents the wave number, φ0 represents the phase distribution on the line sound source, ρ0 and c0 represent the density and sound speed of the medium respectively, and t represents the propagation time.

[0021] Furthermore, in step S3, the process of designing an annular phase screen to perform phase control on the planar sector transducer annular array includes the following sub-steps:

[0022] Using symmetry, the phase distribution φ0 on the line sound source is rotated around the z axis to obtain a two-dimensional phase distribution exist Under the phase control of , the self-bending beams radiated from different azimuth angles generated by the symmetrically distributed sound sources are superimposed to form a sound pressure cavity with the same shape as the segmented broken line Ω′, and are focused at the position of the control target, point Q. They represent the basis in the cylindrical coordinate system respectively;

[0023] According to the material properties of the phase screen, the height distribution of the phase screen is calculated Where c0 represents the sound velocity of the medium between the sound source and the target point, c s Represents the speed of sound of the phase screen material.

[0024] Furthermore, the minimum value of r is not less than 20λ.

[0025] Furthermore, in step S3, the process of performing initial phase encoding on each sector of the transducer array includes the following sub-steps:

[0026] Set the initial phase of the nth sector to φ n :φ n =2πl(n-1) / N, where l represents the topological charge, N represents the total number of sectors of the planar sector transducer annular array, N is greater than 2|lmax|, lmax represents the maximum number of topological charges allowed to be generated by the planar sector transducer annular array, lmax = ±Fix[(N-1) / 2], and Fix() is a rounding function.

[0027] Furthermore, the sound pressure distribution p of the sound field excited by the nth sector is n Expressed as:

[0028]

[0029] Where, φ nrepresents the initial phase of the nth sector, R represents the distance between point P and line element dx, ω=2πf represents the angular frequency; u represents the particle velocity on the line sound source OA; N represents the total number of sectors of the planar sector transducer annular array, L is the radius of the sound source, k s represents the wave number in the phase screen; h represents the height distribution of the phase screen.

[0030] Furthermore, the acoustic fields excited by the phase-encoded N sectors are superimposed to obtain the expected obstacle-avoiding vortex acoustic tweezers, whose sound pressure p* is expressed as:

[0031]

[0032] Beneficial effects:

[0033] The present invention provides a method for constructing a universal obstacle-avoiding vortex acoustic tweezers that can bypass objects of any shape. The method can guide the phased sound waves output by a planar fan-shaped transducer annular array to bypass obstacles of any shape along a set trajectory, and then construct vortex acoustic tweezers with higher positioning accuracy and control capabilities, and minimize the reflection and absorption of sound waves by obstacles, significantly improve the sound pressure and sound radiation force in the focal area of the sound field, and realize precise, flexible and efficient obstacle-avoiding object control, which is of great significance to the development and application of obstacle-avoiding vortex acoustic tweezers technology and obstacle-avoiding object control technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a diagram showing the formation principle of the universal obstacle-avoiding vortex acoustic tweezers proposed in the present invention;

[0035] Figure 2 is the sound pressure distribution diagram under the condition of L=50mm; wherein, (A) is the sound pressure distribution diagram of the self-bending beam in the axial section under the condition of L=50mm; (B) is the sound pressure distribution diagram of the universal obstacle-avoiding vortex acoustic tweezers with l=0 in the axial section under the condition of L=50mm; (C) is the sound pressure distribution diagram of the universal obstacle-avoiding vortex acoustic tweezers with l=0 in the focal plane under the condition of L=50mm; (D) is the phase distribution diagram of the universal obstacle-avoiding vortex acoustic tweezers with l=0 in the focal plane under the condition of L=50mm;

[0036] Figure 3 : are the sound pressure distribution diagrams of the universal obstacle-avoiding vortex acoustic tweezers under the conditions of L = 150 mm and L = 30 mm; wherein, (A) is the sound pressure distribution diagram of the self-bending beam in the axial section under the condition of L = 150 mm; (B) is the sound pressure distribution diagram of the universal obstacle-avoiding vortex acoustic tweezers in the axial section under the condition of L = 150 mm and l = 0; (C) is the sound pressure distribution diagram of the self-bending beam in the axial section under the condition of L = 30 mm; (D) is the sound pressure distribution diagram of the universal obstacle-avoiding vortex acoustic tweezers in the axial section under the condition of L = 30 mm and l = 0;

[0037] Figure 4is the sound pressure distribution diagram of the universal obstacle-avoiding vortex acoustic tweezers with l=1 and l=2; wherein, (A1) is the sound pressure distribution diagram of the universal obstacle-avoiding vortex acoustic tweezers with l=1 in the axial section; (A2) is the sound pressure distribution diagram of the universal obstacle-avoiding vortex acoustic tweezers with l=2 in the axial section; (B1) is the sound pressure distribution diagram of the universal obstacle-avoiding vortex acoustic tweezers with l=1 in the focal plane; (B2) is the sound pressure distribution diagram of the universal obstacle-avoiding vortex acoustic tweezers with l=2 in the focal plane; (C1) is the phase distribution diagram of the universal obstacle-avoiding vortex acoustic tweezers with l=1 in the focal plane; (C2) is the phase distribution diagram of the universal obstacle-avoiding vortex acoustic tweezers with l=2 in the focal plane;

[0038] Figure 5 : These are the sound pressure distribution diagrams of the universal obstacle-avoiding vortex acoustic tweezers with l = 1 in the axial section under the conditions of M = 200, M = 100, and M = 60; wherein, (A) is the sound pressure distribution diagram of the universal obstacle-avoiding vortex acoustic tweezers with l = 1 in the axial section under the condition of M = 200; (B) is the sound pressure distribution diagram of the universal obstacle-avoiding vortex acoustic tweezers with l = 1 in the axial section under the condition of M = 100; (C) is the sound pressure distribution diagram of the universal obstacle-avoiding vortex acoustic tweezers with l = 1 in the axial section under the condition of M = 60;

[0039] Figure 6 This is a diagram of the generation and measurement system of the universal obstacle-avoidance vortex acoustic tweezers;

[0040] Figure 7 Schematic diagram of the sound pressure distribution measurement results of the universal obstacle-avoiding vortex acoustic tweezers with l=0, l=1, and l=2; wherein, (A1) is a schematic diagram of the sound pressure distribution measurement results of the universal obstacle-avoiding vortex acoustic tweezers with l=0 in the axial section; (A2) is a schematic diagram of the sound pressure distribution measurement results of the universal obstacle-avoiding vortex acoustic tweezers with l=1 in the axial section; (A3) is a schematic diagram of the sound pressure distribution measurement results of the universal obstacle-avoiding vortex acoustic tweezers with l=2 in the axial section; (B1) is a schematic diagram of the sound pressure distribution measurement results of the universal obstacle-avoiding vortex acoustic tweezers with l=0 in the focal plane Sound pressure distribution measurement results; (B2) is the sound pressure distribution measurement result of the universal obstacle-avoiding vortex acoustic tweezers with l=1 in the focal plane; (B3) is the sound pressure distribution measurement result of the universal obstacle-avoiding vortex acoustic tweezers with l=2 in the focal plane; (C1) is the phase distribution measurement result of the universal obstacle-avoiding vortex acoustic tweezers with l=0 in the focal plane; (C2) is the phase distribution measurement result of the universal obstacle-avoiding vortex acoustic tweezers with l=1 in the focal plane; (C3) is the phase distribution measurement result of the universal obstacle-avoiding vortex acoustic tweezers with l=2 in the focal plane;

[0041] Figure 8It is a schematic diagram of the formation principle of the semi-Bessel type obstacle-avoiding vortex acoustic tweezers and the sound pressure distribution diagram of the Bessel type obstacle-avoiding vortex acoustic tweezers in the axial section under different conditions; among them, (A) is a schematic diagram of the formation of the semi-Bessel type obstacle-avoiding vortex acoustic tweezers; (B) is the sound pressure distribution diagram of the Bessel type obstacle-avoiding vortex acoustic tweezers in the axial section under the condition of L=50mm; (C) is the sound pressure distribution diagram of the Bessel type obstacle-avoiding vortex acoustic tweezers in the axial section under the condition of L=150mm; (D) is the axial sound pressure distribution diagram of the universal and semi-Bessel type obstacle-avoiding vortex acoustic tweezers. DETAILED DESCRIPTION

[0042] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0043] This embodiment discloses a method for constructing a universal obstacle-avoiding vortex acoustic tweezers that can bypass objects of any shape. The method comprises the following steps:

[0044] S1, for obstacles with arbitrary shapes, a segmented broken line circumscribed to their contours is designed to construct a self-bending beam trajectory.

[0045] S2, based on the caustic theory, designs the initial phase distribution of the one-dimensional line sound source according to the position of each line segment in the segmented broken line to form a self-bending beam with a preset curved propagation trajectory.

[0046] S3, rotate the phase distribution of the one-dimensional line sound source in step S2 along the axis to construct a two-dimensional phase distribution, design an annular phase screen to control the phase of the planar sector transducer annular array, perform initial phase encoding on each sector of the transducer array, and form a universal obstacle-avoiding vortex acoustic tweezers that can bypass objects of any shape.

[0047] like Figure 1 As shown in the figure, assume a planar sector transducer annular array is placed in the xoy plane, with the control target located at point Q. An obstacle with a profile of Ω is placed on the z-axis, blocking the sound source and point Q. First, the phase of the line sound source OA on the x-axis is manipulated to form a self-bending beam that can bypass the obstacle and propagate to point Q.

[0048] By drawing tangent lines on M randomly distributed points on the curve Ω, a segmented polyline Ω′ can be formed, which contains M line segments, and Ω′ is completely outside Ω. Among them, the mth and m+1th line segments P′ m-1 P′ m and P′ m P′ m+1 Tangent to Ω at point P m and P m+1 The intersection points of the two line segments and the x-axis are S m and S m+1If all points on the sound source OA radiate sound waves with the same initial phase, then for S m and S m+1 Two points, the spherical wave excited by them is at P m and P m+1 The phase of the point can be expressed as Φ m and Φ m+1 , the phase difference satisfies the recursive relationship Φ m+1 -Φ m =k0(D m+1 -D m ), where D m and D m+1 They are line segments P m S m and P m+1 S m+1 When M is large enough, the line segment P′ m-1 P′ m and P′ m P′ m+1 Equivalent to point P m and P m+1 According to the caustic principle, point S on the sound source needs to be m Perform the following initial phase compensation to form a self-bending beam:

[0049]

[0050] If the length of the sound source is L, S m The average interval of the sequence, that is, the average phase control accuracy of the sound source can be expressed as L / M. According to the sampling theorem, the phase of the sound source should be controlled with an accuracy of no less than λ / 2, that is, M should be no less than At the same time, according to the relevant research conclusions of self-bending beams, L should be no less than 20λ.

[0051] Due to S m It is discontinuously distributed. In order to make the initial phase of the sound source continuous, the phase control with the initial phase of φ0(x) can be performed on any point on OA, where φ0(x) is the sequence φ m The upsampling result.

[0052] On this basis, the sound pressure of the self-bending beam generated by the initial phase control of the one-dimensional line sound source OA at any point P in space can be expressed as:

[0053]

[0054] Where u represents the particle velocity on the line sound source OA, R represents the distance between point P and the line element dx, and ω = 2πf represents the angular frequency.

[0055] Furthermore, by rotating the above one-dimensional phase distribution φ0(x) around the z-axis, the two-dimensional phase distribution of the planar sector transducer annular array can be obtained. exist Under phase control, the self-bending beams radiated from different azimuth angles by the symmetrically distributed sound sources can be superimposed to form a sound pressure cavity with a shape consistent with Ω′, and focus at the Q position. This two-dimensional phase control can be achieved by installing an annular phase screen on the planar sector transducer annular array. According to the material properties of the phase screen, its height distribution can be expressed as:

[0056]

[0057] Where f represents the operating frequency of the transducer, c0 represents the sound velocity of the medium between the sound source and the target point, and c s Represents the speed of sound within the material.

[0058] Then, in order to generate topological charge controllable obstacle-avoiding vortex acoustic tweezers, the initial phase of the nth sector of the planar sector transducer ring array is set to φ n =2πl(n-1) / N, where l represents the topological charge. Based on research on vortex acoustic beams, a planar sector transducer annular array with N sectors can generate obstacle-avoiding vortex acoustic tweezers with a maximum topological charge of lmax=±Fix[(N-1) / 2], where Fix() is a rounding function. Therefore, the number of sectors N should be greater than 2|lmax|.

[0059] After the above phase encoding, the sound pressure distribution of the sound field excited by the nth sector can be expressed as:

[0060]

[0061] By superimposing the acoustic fields excited by the N phase-encoded sectors, the expected obstacle-avoiding vortex acoustic tweezers can be obtained, and its sound pressure can be expressed as:

[0062]

[0063] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0064] Example:

[0065] like Figure 1 As shown, let the profile Ω of a non-spherical obstacle satisfy the following piecewise function:

[0066]

[0067] The target point Q is set directly above the obstacle with coordinates of (0, 0, 45) mm. Based on the method proposed in this invention, the obstacle outline Ω is evenly divided with the condition of M = 300, and a broken line Ω' is constructed to approximate the obstacle outline, and the initial phase distribution φ0 of the outgoing sound source is solved. The parameters are set to f = 1 MHz, c0 = 1500 m / s, and ρ0 = 1000 kg / m 3 , c s =2316.6m / s,ρ s =1050kg / m 3 , a self-bending beam and obstacle-avoiding vortex acoustic tweezers were formed under the condition that the radius of the planar fan-shaped transducer ring array was 50 mm. Figure 2 (A) shows the sound pressure distribution of the self-bending beam formed by the phase-controlled line sound source in the axial section, where the preset trajectory Ω' is marked by a white dotted line. It can be observed that the sound waves excited by the line sound source form a clear curved trajectory and an elliptical main lobe, and the sound pressure peak point of the main lobe is located at (15.0, 34.1) mm. Since the length of the sound source is only 50 mm, the end point of the sound source is tangent to the preset trajectory at (10.8, 40.4) mm, so that the top of the preset curve cannot form an acoustic caustic line with the sound source. Therefore, in the sound pressure distribution formed, although the lower half of the curved trajectory forms a good match with the white curve, the upper half of the trajectory deviates from the preset curve. In order to measure the degree of matching between the two, the angle between the gradient direction of the sound pressure peak point in the main lobe and the x-axis is defined as the characteristic angle θ of the self-bending beam formed. b When L = 50 mm, the characteristic angle θ of the self-bending beam is b The self-bending beam is rotated around the z axis to obtain an obstacle-avoiding vortex acoustic tweezer with l = 0. Figure 2 (B) shows the acoustic pressure distribution of the obstacle-avoiding vortex acoustic tweezers in an axial cross-section with l = 0. It can be observed that the acoustic pressure distribution exhibits an inverted teardrop-shaped acoustic pressure cavity formed by the superposition of curved trajectories. At z = 59.3 mm above the cavity, the main lobes of the self-bending beams superimpose to form an elliptical focal zone with an axial -6 dB width of 15.6 mm. Similarly, due to the length of the sound source, the focal zone is located slightly above the intersection of the white dashed lines. Figure 2 (C) and Figure 2 Figure (D) shows the sound pressure and phase distribution of the obstacle-avoiding vortex acoustic tweezers within the cross-section (focal plane) at z = 59.3 mm. The sound pressure distribution within the focal plane is characterized by concentric pressure rings and a high-pressure circular spot with a diameter of 1.32 mm at -6 dB, while the phase distribution exhibits a non-spiral pattern.

[0068] Then, the radius of the planar sector transducer annular array was changed to 30 mm and 150 mm respectively, forming the corresponding self-bending beam and obstacle-avoiding vortex acoustic tweezers. Figure 3 (A) shows the sound pressure distribution of the self-bending beam formed by the annular array of planar sector transducers with a radius of 150mm in the axial section. As the length of the sound source becomes longer, the sound waves emitted from the far end of the sound source can be tangent to the upper half of Ω', forming a caustic line. Therefore, the self-bending beam formed is obviously more consistent with the preset trajectory Ω'. Among them, the main lobe sound pressure peak point rises to (8.5,44)mm, θ b The corresponding sound pressure distribution of the obstacle avoidance vortex acoustic tweezers in the axial section is as follows: Figure 3 As shown in (B), the focal zone formed is located at z = 49mm, and the -6dB axial width is 4.5mm, which is significantly closer to Q than the case of L = 50mm. This shows that the increase in the radius of the fan-shaped transducer helps to improve the accuracy and axial resolution of the obstacle avoidance vortex acoustic tweezers. The sound pressure distribution in the axial section of the self-bending beam formed by the planar fan-shaped transducer annular array with a radius of 30mm is shown in the figure. Figure 3 As shown in (C), it can be seen that although the bottom of the self-bending beam forms a good consistency with the preset trajectory, due to the shortening of the sound source length, the top of the preset trajectory cannot form a caustic line with the sound source. Therefore, the position of the peak point of the sound pressure is significantly lower than that of the case of L = 50 mm, and is reduced to (18.3, 28.2) mm. The characteristic angle θ b Then it increases to 80.9°. The sound pressure distribution of the obstacle avoidance vortex acoustic tweezers formed under the condition of L = 30mm in the axial section is shown as follows Figure 3 As shown in (D). It can be seen that the top of the acoustic pressure cavity profile of the obstacle-avoiding vortex acoustic tweezers formed deviates significantly from the preset trajectory, and the focal area is formed at a height of z = 82 mm, which is much higher than the preset position, and the axial width is significantly widened. Therefore, it can be considered that when the transducer radius is less than 30 mm (20λ), the zero-sound pressure cavity morphology of the obstacle-avoiding vortex acoustic tweezers formed deviates significantly from the expected value, and it is impossible to achieve obstacle avoidance object manipulation at a predetermined position.

[0069] Then, let Δφ be π / 8 and π / 4 respectively, and the obstacle-avoiding vortex acoustic tweezers with l=1 and 2 are formed. Figure 4 As shown in Figures (A1) and (A2), under the conditions of l = 1 and 2, the obstacle-avoiding vortex acoustic tweezers formed an inverted water droplet-shaped sound pressure cavity in the axial section, and due to the spiral phase encoding of the sound source, a hollow focal area was formed at a height of z = 49 mm. Figure 4 (B1), (B2) and Figure 4As shown in (C1) and (C2), within the cross section of z = 49 mm, the obstacle-avoiding vortex acoustic tweezers present an annular sound pressure distribution and a spiral phase distribution. Among them, the radius of the sound pressure ring formed by the obstacle-avoiding vortex acoustic tweezers with l = 1 and 2 are 1.66 and 2.16 mm respectively, showing a trend of increasing with the increase of topological charge. This shows that although the size of the obstacle-avoiding vortex acoustic tweezers formed changes with the change of topological charge, the shape of its obstacle-avoiding cavity remains basically unchanged, and it can achieve control of targets of different sizes while avoiding obstacles.

[0070] Then, let M = 200, 100, and 60 respectively, and construct segmented polylines with different numbers of segments for the non-spherical obstacle Ω, and form obstacle-avoiding vortex acoustic tweezers with l = 1 under different phase control accuracies. Figure 5 As shown in (A), the sound pressure distribution of the vortex acoustic tweezers formed under the condition of M = 200 is basically the same as that under the condition of M = 300. The characteristics such as the hollow focal area and the inverted water droplet-shaped acoustic pressure cavity are reflected in the sound pressure distribution. As the number of M decreases, the height of the focal area increases to z = 60.3 mm, which is slightly higher than the case of M = 300. The sound pressure distribution of the vortex acoustic tweezers formed under the conditions of M = 100 and M = 60 in the axial section are shown as follows: Figure 5 As shown in (B) and (C). When M = 100, the height of the focal region is further increased to z = 65.9 mm, and obvious noise is reflected in the sound pressure distribution in the near field and off-axis regions. This shows that as M decreases, the phase control resolution of the sound source decreases, and the quality of the vortex acoustic tweezers formed also decreases. As M further decreases to 60, the height of the hollow focal region of the vortex acoustic tweezers increases to z = 76.3 mm, the focal region sound pressure decreases significantly, and the noise in the near field and off-axis regions is significantly enhanced. At the same time, the sound pressure distribution below the hollow focal region no longer appears as a zero sound pressure cavity, but due to diffraction, obvious secondary vortices are generated. Therefore, it can be considered that under the condition of M < 60, that is, when the average phase control accuracy of the sound source is lower than λ / 2, the morphology of the obstacle avoidance vortex acoustic tweezers formed deviates greatly from expectations, and it is impossible to achieve obstacle avoidance object manipulation at a given position.

[0071] Furthermore, we built Figure 6The obstacle avoidance vortex acoustic tweezers generation and measurement system shown in the figure. A planar sector transducer annular array with 16 sectors and a frequency of 1 MHz is fixed in a water tank. M is set to 300, a broken line Ω' is designed for non-spherical obstacles, and a ring phase screen for initial phase control is fabricated using 3D printing technology and mounted on the transducer surface. Under computer control, an FPGA generates 16 square waves with controllable initial phases. After power amplification and filtering, these waves drive the planar sector transducer annular array to generate obstacle avoidance vortex acoustic tweezers underwater with topological charges of 0, 1, and 2. Simultaneously, a needle hydrophone is fixed to a stepper motor, and three-dimensional scanning of the sound field is achieved under the control of the stepper motor controller. The hydrophone received signal is amplified by a preamplifier, acquired by an oscilloscope, and transmitted to a computer for post-processing.

[0072] The obstacle avoidance vortex acoustic tweezers formed were measured using the above system, such as Figure 7 As shown in (A1), (A2) and (A3), the obstacle-avoiding vortex acoustic tweezers with l = 0, 1, and 2 all present the expected sound pressure cavity in the axial section. Among them, the obstacle-avoiding vortex acoustic tweezers with l = 0 form an elliptical focal zone at the expected position, while the obstacle-avoiding vortex acoustic tweezers with l = 1 and 2 form a hollow focal zone at the corresponding height. Figure 7 As shown in (B1), (B2), (B3), (C1), (C2) and (C3), in the focal plane, the measurement results of the obstacle-avoiding vortex acoustic tweezers with l = 0, 1, 2 are also consistent with Figure 2 and Figure 4 The results are consistent with those in

[15] . The obstacle-avoiding vortex acoustic tweezers with l = 0 form a central sound pressure spot and concentric sound pressure rings in the focal plane, exhibiting a non-spiral phase distribution. However, the obstacle-avoiding vortex acoustic tweezers with l = 1 and 2 exhibit concentric ring-shaped sound pressure distributions and spiral phase distributions in the focal plane, confirming the formation of obstacle-avoiding vortex acoustic tweezers with different topological charges.

[0073] The universal obstacle avoidance vortex acoustic tweezers formed by the method proposed in the present invention are compared with the obstacle avoidance vortex acoustic tweezers constructed based on semi-Bessel waves (transverse self-accelerating waves specifically used to form circular arc trajectories). In order to better distinguish the two, the obstacle avoidance vortex acoustic tweezers formed based on semi-Bessel waves are called semi-Bessel type obstacle avoidance vortex acoustic tweezers. Figure 8 As shown in (A), in order to enable the semi-Bessel obstacle-avoiding vortex acoustic tweezers to also bypass non-spherical obstacles, a circular arc trajectory with a radius of 71.6mm is designed. Limited by the set trajectory, the area of r<24mm in the sound source is set as the zero sound pressure area. Let l=0, and perform semi-Bessel phase control on the planar fan-shaped transducer annular array with a radius of 50 and 150mm, respectively, to form a semi-Bessel obstacle-avoiding vortex acoustic tweezers. Figure 8As shown in (B) and (C), under both conditions, the semi-Bessel type obstacle avoidance vortex acoustic tweezers formed produced a bullet-shaped sound pressure cavity and an elliptical focal area, with the focal area at heights of 59.5 and 55 mm respectively. In order to better reflect the difference between the general type and the semi-Bessel type obstacle avoidance vortex acoustic tweezers, the axial sound pressure distribution of the two was compared, and the results are shown in Figure 1. Figure 8 As shown in (D). It can be seen that under the conditions that the sound source radius is 50 and 150 mm respectively, the focal area of the universal obstacle avoidance vortex acoustic tweezers is located at 49.0 and 59.3 mm respectively, which are closer to the predetermined position Q than the focal area of the semi-Bessel obstacle avoidance vortex acoustic tweezers under the same conditions. At the same time, since the area of the sound source r<24 mm is designed as a zero sound pressure area during the semi-Bessel phase control process, the maximum sound pressure gains of the semi-Bessel obstacle avoidance vortex acoustic tweezers formed are 27.8 and 226.5 respectively. For the universal obstacle avoidance vortex acoustic tweezers, since the entire sound source is used, under the conditions of L=50 and 150 mm, the maximum sound pressure gains are 40.9 and 369.7 respectively, which are much larger than the maximum sound pressure gain of the semi-Bessel obstacle avoidance vortex acoustic tweezers. It can be seen that the construction method proposed in the present invention has significant advantages in the formation accuracy and efficiency of the obstacle avoidance vortex acoustic tweezers.

[0074] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions based on the principles of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for constructing a universal obstacle-avoiding vortex acoustic tweezers capable of bypassing objects of any shape, characterized in that: The method for constructing the universal obstacle-avoiding vortex acoustic tweezers comprises the following steps: S1, for obstacles with arbitrary shapes, a segmented polyline circumscribed to their contours is designed to construct a self-bending beam trajectory; S2, based on the caustic theory, designs the initial phase distribution of the one-dimensional line sound source according to the position of each line segment in the segmented polyline, forming a self-bending beam with a preset curved propagation trajectory; S3, rotating the phase distribution of the one-dimensional line sound source in step S2 along the axis to construct a two-dimensional phase distribution, designing an annular phase screen to control the phase of the planar sector transducer annular array, performing initial phase encoding on each sector of the transducer array, and forming a universal obstacle-avoiding vortex acoustic tweezers that can bypass objects of any shape; In step S1, the process of constructing the self-bending beam trajectory includes the following sub-steps: Randomly select M points on the known obstacle contour trajectory Ω and draw tangents to the obstacle contour trajectory Ω through these points; Connect adjacent tangents to obtain a segmented broken line Ω′ containing M segments, which is completely tangent to Ω. The segmented broken line Ω′ is completely outside the obstacle contour trajectory Ω. The larger M is, the higher the matching degree between the obstacle avoidance cavity and the obstacle contour is. M is not less than Where L is the radius of the sound source and λ is the wavelength; In step S2, the process of designing the initial phase distribution of the one-dimensional line sound source according to the position of each line segment in the segmented polyline includes the following sub-steps: According to the segmented broken line Ω′, calculate the intersection S of the tangent line of the mth segment and the sound source m ; Based on the caustic method, calculate S m The initial phase sequence φ corresponding to the sequence m :φ m =-k0D m , where k0 represents the wave number, D m Represents the mth line segment and S m The distance between points; The discontinuous distribution S m Continuation, specifically, the initial phase sequence φ m Upsampling is performed to obtain the initial phase distribution of any point on the line sound source.

2. The method for constructing a universal obstacle-avoiding vortex acoustic tweezers capable of bypassing objects of any shape according to claim 1, characterized in that: The sound pressure p of the self-bending beam generated by the initial phase control of the one-dimensional line sound source at any point P in space is expressed as: Where u represents the particle velocity on the line sound source, R represents the distance between point P and the line element dx, ω = 2πf represents the angular frequency, L is the radius of the sound source, k0 represents the wave number, φ0 represents the phase distribution on the line sound source, ρ0 and c0 represent the density and sound speed of the medium respectively, and t represents the propagation time.

3. The method for constructing a universal obstacle-avoiding vortex acoustic tweezers capable of bypassing objects of any shape according to claim 1, characterized in that: In step S3, the process of designing an annular phase screen to perform phase control on the planar sector transducer annular array includes the following sub-steps: Using symmetry, the phase distribution φ0 on the line sound source is rotated around the z axis to obtain a two-dimensional phase distribution exist Under the phase control of , the self-bending beams radiated from different azimuth angles generated by the symmetrically distributed sound sources are superimposed to form a sound pressure cavity with the same shape as the segmented broken line Ω′, and are focused at the position of the control target, point Q. They represent the basis in the cylindrical coordinate system respectively; According to the material properties of the phase screen, the height distribution of the phase screen is calculated Where c0 represents the sound velocity of the medium between the sound source and the target point, c s Represents the speed of sound of the phase screen material.

4. The method for constructing a universal obstacle-avoiding vortex acoustic tweezers capable of bypassing objects of any shape according to claim 3, characterized in that: The minimum value of r is not less than 20λ.

5. The method for constructing a universal obstacle-avoiding vortex acoustic tweezers capable of bypassing objects of any shape according to claim 1, characterized in that: In step S3, the process of performing initial phase encoding on each sector of the transducer array includes the following sub-steps: Set the initial phase of the nth sector to φ n :φ n =2πl(n-1) / N, where l represents the topological charge, N represents the total number of sectors of the planar sector transducer annular array, N is greater than 2|lmax|, lmax represents the maximum number of topological charges allowed to be generated by the planar sector transducer annular array, lmax = ±Fix[(N-1) / 2], and Fix() is a rounding function.

6. The method for constructing a universal obstacle-avoiding vortex acoustic tweezers capable of bypassing objects of any shape according to claim 3, characterized in that: The sound pressure distribution p of the sound field excited by the nth sector n Expressed as: Where, φ n represents the initial phase of the nth sector; N represents the total number of sectors of the planar sector transducer annular array, k s represents the wave number in the phase screen; h represents the height distribution of the phase screen.

7. The method for constructing a universal obstacle-avoiding vortex acoustic tweezers capable of bypassing objects of any shape according to claim 6, characterized in that: The acoustic fields excited by the phase-encoded N sectors are superimposed to obtain the expected obstacle-avoiding vortex acoustic tweezers, whose sound pressure p* is expressed as:

Images